1. Field of the Invention
The present invention relates to a storage device having a function for coping with a computer virus that has the ability to prevent infection with a computer virus and to properly deal with infection with a computer virus.
In recent years, computer systems using computer programs have prevailed in enterprises, households, and the like. Accordingly, the number of occurrences of computer viruses that destroy or damage the computer systems and that have an auto-proliferation ability has tended to increase markedly.
In particular, recently-procurable personal computers are interconnected over a network such as a local area network (LAN) and adopt the configuration enabling information exchange through data communications. The fear that a computer virus (hereinafter abbreviated to a virus) residing in one personal computer spreads into the other personal computers connected over the network is becoming more and more serious.
This makes it necessary to construct a storage device having the ability to freely use files while preventing the breeding of a virus and to delete a file infected with a virus or restore the infected file into an uninfected state.
2. Description of the Related Art
For a clear understanding of problems concerning viruses destroying computer systems, infection with a virus in a typical storage device will be described with reference to FIG. 1.
A storage device 100 basically comprises, as shown in FIG. 1, a disk 105 for storing files, and a controller 120 for executing driving control for the disk 105 and also executing input/output control for a personal computer 110 that is connected to the drive.
The storage device 100 having the foregoing components is designed to be directly accessed by a driver under the control of an operating system in the personal computer 110 comprising a CPU 112 for processing various kinds of data, a RAM 114 for storing various kinds of data and programs, a ROM 116, and the like. In other words, the storage device yields such an environment in which; a file expanded in the personal computer 110, one running can readily destroy other files stored in the storage device.
On the other hand, a virus that intrudes from an external unit into a file via a LAN adapter 130, keyboard 140, display 150, or the like rewrites another file using a physical address of the file which is indicated by low-order address bits, or rewrites a system startup area such as a bootstrap using a physical address of the system startup area which is indicated by low-order address bits, and thus destroys an original program.
This poses a problem that files stored in a storage device are readily infected with a virus.
In an effort to cope with the above problem, a prior art system design is adopted such that if a virus checker (not shown) expanded in the personal computer 110 finds a file infected with a virus from among files expanded on the disk 105 in the storage device 100, all the files expanded on the disk are cleared and then originals of the files are installed again.
However, in the prior art, it is detected whether any of the files expanded on a disk in a storage device is infected with a virus. If any of the files is infected, the file is treated properly. The prior art does not adopt a method of actively preventing infection with a virus. There is therefore a problem that files expanded on the disk in the storage device are readily infected with a virus.
Moreover, in the prior art, when it is detected that any of files expanded on a disk in a storage device is infected with a virus, all the files expanded on the disk are cleared and then originals of the files are installed again. This poses a problem that a user is obliged to incur an enormous work load.
In the prior art, a file judged to be infected with a virus is cleared in its entirety. It cannot be analyzed as to what kind of virus destroyed the file. This poses a problem in that an anti-virus measure cannot be examined.